I have an eastward facing sliding glass door in my bedroom. During the morning, the beating California sun cooks the room, raising it to 80-90 degrees F (26-32 Celsius) by 9 AM. While the blinds don't block all of the light, they do a good enough job that I'm worried the heat is coming from the large air gap between the glass and blinds (given the size of the door/window), and/or that the flip side of the blinds are being cooked (as evident by them looking burnt), which then emit heat into the room.

I've thought of blackout curtains, but the current blinds are already doing a mostly okay job with the light. The blackout curtains wouldn't eliminate the air gap between the glass and them, and would presumably be cooked by the sun in lieu of the blinds (or not help in that regard if I put them over the blinds rather than replacing them). I could also leave the bedroom door open at night to get better circulation, but then this ends up warming the rest of the house. I'd prefer to keep it out from the beginning.

Are there any in between steps I can take to reduce the heat gain short of replacing the entire glass pane with tinted/multi-pane w/ heat-resistant gas or replacing the whole door?

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  • 4
    There are window films or an awning, but guessing the sun shines straight at the window so an awning won't work till later in the day. A window film that reflects the sun might be the best bet to keep cool.
    – crip659
    Jun 20, 2022 at 17:31

4 Answers 4


The blinds absorb energy from the sun, but your problem is... they're inside. So the sun just heats the blinds, which then heat the room. Blinds or curtains make the room darker, but they do nothing for heat.

If you don't want your room to heat in the morning, then whatever will block the sunlight needs to be outside, so it can release the resulting heat outside.

An awning would work if the window faced south, because sunlight from the South comes from above. But sunlight from the East comes in horizontally, so it would just go under the awning and through the window.

Here's a suggestion:

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These are outside, so they release the heat to outside air. There are plenty of holes for ventilation, so the air between the shutter and the window won't get to a high temperature.

Another option:

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It's a neater package, rolling back in the box when not in use. These normally have small holes between the horizontal strips for ventilation, but that's not as effective as the shutters shown above, so the space between the rolling shutter and the window will be hotter, so more heat will pass through the window. Picking them in white instead of a dark color somewhat mitigates that...

Then there's that, it's just a rolling blind, but it's outside.

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From the picture it looks like you have a balcony, so maybe you could fit a cheap indoors rolling blind outside, that wouldn't be exposed to rain. It should be white to stay cool, and have a bit of space left on top of the roll so the hot air can circulate and not remain trapped between it and the window.

  • 1
    There are also exterior metal roller shades that can roll up into a neat tidy package - not cheap though. Jun 21, 2022 at 6:42
  • @FreshCodemonger can you post a link for those metal rollers
    – Traveler
    Jun 21, 2022 at 7:41
  • 1
    @FreshCodemonger I've added some of that to the answer. I think they're called "roller shutters"
    – bobflux
    Jun 21, 2022 at 9:31

Since you have so much heat coming in, you either do not have dual pane glass, or the seal between the glass is leaking, otherwise you would not feel the heat.

Few ways to block the sun. Depending if you are Renting or owning.

First of all that curtain you have is not very good for that.

You can install new curtains to fully block the sun but the heat will still come true the window glass.

On the outside, you could install awning, but since it is east side, it wont block morning sun.

Insulate the glass itself.

Pro, it blocks the sun with high efficiency.

Pro: You are invisible to anyone from the street.

Con, it will Permanently darken your windows.

It is relatively easy to install it your self, it is basically glued to the window from inside. It can be removed, scraped.

The product:

One Way Mirror Glass Tint Heat Control Sun UV Blocking Door Sticker Reflective Foil.

They come in two versions.

Interior and Exterior application. They also come in clear or colors.


Here is how it looks installed

enter image description here

If you are renting, Foil is the way to go, it can be removed.

There are easy to follow instructions for DIY

  • You need to be careful with products installed on the inside. The heat can end up being trapped in the air gap of the glazing unit and cause the seals to fail. Jun 21, 2022 at 6:41
  • 1
    No, no, you install it on the outside. Well, I have some and it said to use it on the ouitside, becasue if you put it on the inside it can heat the glass and make it crack. Highly recommended, by the way.
    – RedSonja
    Jun 21, 2022 at 8:08
  • @RedSonja can you provide the link of the product you are taking about
    – Traveler
    Jun 21, 2022 at 8:10
  • 2
    I have mine installed on the inside. It's never been any issue, so far. I'd need a crane to get it on the outside ;) [Had it been a simple task to walk out onto a balcony, I'd have done the outside.] One thing to note when installing this - they don't warn you of its cussed propensity for sticking to itself. Be very prepared for this.
    – Tetsujin
    Jun 21, 2022 at 10:56
  • 1
    @Tetsujin oh my goodness yes. I had the neighbours in stitches watching me tangled in the stuff. And it still has one tiny wrinkle (which only I can see.) I would recommend getting help to installation.
    – RedSonja
    Jun 22, 2022 at 8:16

It's no use blocking the heat inside, it's already got in. You have to stop the sun from hitting the glass.

Just about all German houses have external window blinds which you can roll up and down with a band or a winding handle. I have seen electric ones with remote control and wifi connection. These things are sturdy enough to block winter storms as well as 35 degree sun.

Installation is non-trivial. Depending on quality there is a box to hold the rolled-up blind, and rails where it slides down, to keep it in place and protect it from side-wind. You get what you pay for.

I can't access your area to show you examples, but if you google "external window blinds" and "roller shutters" and "outdoor venetian blinds" you will see what I mean. Obviously these are more expensive than curtains. But they are well worth it IMHO.

  • This is great. But you will need to install special frame on the outside for the roller shade.
    – Traveler
    Jun 21, 2022 at 8:38

One option is to use special insulating cloth as a curtain backer, and hang it so it's as close to the window as possible, and so it reaches right down to either the floor or the window sill, if there is one, and it sticks out significantly. I read in a Cornell Cooperative Extension pamphlet years ago that the basic idea here is to prevent air channels from forming.

I have consistently found this cloth at Jo-Ann Fabrics over the years. It might be called "Drapery Lining & Blackout Fabric" -- I can't be sure, looking at it on the screen.

This fabric is white and costs at most $10 a yard.

The way I've used it is, I pair it with something with color, and hang it by folding the top over some thin wooden molding, and screw the ends of the molding into the wall with anchors if I'm not right at a stud.

For example, I paired one with an Indian bedspread. That was a living room. Another one, I used panels of sheer light blue fabric, not as wide as the white liner. That gave the effect of something light and airy, that looks like it might start billowing in the breeze.

Since there won't be any pleats or curtain rod or anything, you will want to screw an L on the side, about halfway or two-thirds of the way up, so you can pull the curtain to the side and rest it on the L when you want daylight to come in. You might need to give the curtain (both layers, of course) a bit of a twist so that it doesn't pop out of the L.

Alternatively you could use cellular blinds, the "light blocking" or "blackout" kind.

Either of these options will help in both summer and winter.

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